OPHIUROIDEA 183 



rather sluggish animals. The development is unknown, excepting 

 that some few of them {Ophiomitrella davigera and OjyJiiacantha 

 anomala, among British species) are viviparous (and hermaphro- 

 dites). One species, Ophiacantha bidentata, is known to be phos- 

 phorescent ; it may well be supposed that this will hold good for 

 several more of them. 



Four genera are known to be represented in British seas, but 

 several more have been found in the North Atlantic, and may- 

 be expected to occur also in the deep-sea off the British coasts, 

 viz. OphiopUnthaca Verrill, with the species 0. carduus (Lyman) 

 (25° 49' N., 20° 12' W., 3015 m., " Challenger " ; 30° 17' N., 

 43° 7' W., 3500 m., " TaUsman "), and 0. chelys Lyman 

 (30° 38' N., 20° 12' W., 3015 m., "Challenger" ; 39° 48' N., 

 12° 12' W., 3307 m., " Talisman " ; 40° 58' N., 9° 40' W., 2271 m., 

 " Princesse Alice ") ; Opliiothamnus Lyman, with the species 



0. affinis Ljungman (Syn. OphiopUnthaca occlusa Koehler ; 

 Ophioleda minima Koehler) (Bay of Biscay to off Madeira, 1220- 

 1425 m., " Josephina ", " Talisman ", " Princesse AHce ") ; 

 Ophicamax Lyman, with the species 0. dominans Koehler (25° 29' 

 N., 18° 22' W., 882 m., " TaUsman ") ; Ophiomedea Koehler, 

 with the species 0. duplicata Koehler (29° 52' N., 14° 4' W., 2075 

 m., " TaUsman " ; only one specimen known) ; Ophiotrema 

 Koehler, with the species 0. Alberti Koehler (38° 08' N., 23° 19' 

 W., 4020 m., '' Princesse Alice " ; 42° 19' N., 23° 36' W., 4060 m., 

 " Talisman " ; also 51° T S., 9° 31' W., 3785 m., " Scotia ") ; 

 Ophiomyces Lyman, with the species O.frutectosus Lyman (Azores, 

 575-1080 m., Josefina Bank, 210-410 m.,'' Josefina "), and 0. 

 grandis Lyman (Bay of Biscay, 392-608 m., " Talisman ") ; 

 Ophiolebes Lyman, with the species 0. bacata Koehler (32° 35' N., 

 17° 05' W., 1700 m., " Princesse Alice " ; only one specimen 

 known), and 0. retecta (Koehler) (Syn. Ophioscolex retectus 

 Koehler) (Bay of Biscay, 1410 m., " Caudan " ; only one specimen 

 known). The main characters of these genera are given in the 

 following key to the genera of the family Ophiacanthidae. 



Key to the genera of Ophiacanthidce known from or likely to 

 occur in the British seas. 



1. Radial shields usually large and distinct, mostly naked ; rarely 



they are smaller and confined to edge of disk, in which case 



the scales carry large, globular stumps or granules . . 2 



Radial shields small, but distinct ; scales of disk not with globular 



stumps or granules ....... 5 



Radial shields totally covered by spines or scales, or by a thick 



skin, at most the outer end naked (in Ophiotoma, see Fig. 104) 6 



